FR3080171A1 - CAPILLARY PUMP HEATING PUMP WITH IMPROVED OPERATION - Google Patents

Abstract

A capillary pumping heat pipe having a first end for heating and a second end for cooling, and a sealed enclosure extending between the first end and the second end, the enclosure comprising a stack of plates (12, 14, 16), said stack comprising two closure plates (12), and spacer plates (14, 16) between the closure plates (12), each intermediate plate (14, 16) having an opening whose edges partially delimit a channel (8). The openings of at least three spacer plates (14, 16) are dimensioned such that they define grooves (10) extending between the first end and the second end of the heat pipe, the grooves (10) having a width in a direction of the stack is less than the depth in the direction of the plane of the plates (14, 16).

Description

HOT PUMP HEATER WITH IMPROVED OPERATION DESCRIPTION

TECHNICAL AREA AND PRIOR ART

The present invention relates to an improved functioning capillary pumped heat pipe.

The invention belongs to the field of heat exchange devices, in particular heat pipes, more particularly capillary pumped heat pipes.

A heat pipe has a hermetically sealed enclosure, a working fluid and a capillary network. During manufacturing, all the air present in the heat pipe is evacuated and a quantity of liquid is introduced allowing the capillary network to be saturated. There is then an equilibrium between the liquid phase and the vapor phase.

Under the effect of a heat source applied to one of the ends, designated evaporator, the liquid vaporizes by inducing a slight overpressure which causes the movement of the vapor towards the second end, designated condenser. At the condenser, the vapor condenses and returns to the liquid phase. The condensed fluid circulates in the capillary network and returns to the evaporator under the effect of capillary forces. The return of the liquid fluid from the condenser zone to the evaporator zone is obtained by capillary pumping.

The grooved heat pipes operate on the principle of capillary pumping. They have a tube in which the inner surface has longitudinal or slightly spiral-shaped grooves. Grooved heat pipes have a vapor core and a capillary network in which the liquid circulates. Due to a variation in curvature of the vapor-liquid interface between the condenser zone and the evaporator zone, a pressure gradient appears in the liquid, which leads to a variation in capillary pressure. The smaller the width of the grooves, the greater the capillary pumping effect.

Furthermore, deep grooves make it possible to obtain a large passage section for the liquid return, and therefore to minimize the pressure loss.

The maximum power that can be transported by grooved heat pipes is generally fixed by the capillary limit whose motor term is capillary pressure, and the term essentially limiting the loss of liquid pressure in the grooves.

However, the techniques for producing the state of the art of these heat pipes do not make it possible to obtain grooves having a depth substantially greater than their width.

These heat pipes can be produced by extrusion. With such a technique, the depth to width ratio is of the order of 1. In addition, the bottom of the grooves has rounded corners, which does not allow good capillary action in the corners.

Another technique uses mechanical machining, with this technique also the depth to width ratio is not significantly greater than 1.

Another technique uses chemical etching. But it also does not allow a significant depth to width ratio. In addition, the corners of the bottom of the grooves are rounded.

Document US 7 051793 describes a heat pipe comprising one or more zones of circulation of the fluid in vapor form and on either side of these zones porous zones of circulation of the liquid, these capillary zones extending over the whole heat pipe.

The heat pipe is made by stacking plates. The capillary zones are obtained by stacking plates comprising windows, the windows having orthogonal directions from one plate to another.

The pumping effect is not optimal. In addition, a large pressure drop exists. This heat pipe spreads the heat flow over the width of the heat pipe and is not optimized for the transport of the heat flow along its length.

STATEMENT OF THE INVENTION

It is therefore an object of the present invention to provide a capillary pump heat pipe with improved operation.

It is also an additional object of the present invention to provide a capillary pump heat pipe of simplified embodiment.

The goals set out above are achieved by a heat pipe comprising a stack of plates joined together in a hermetic manner. The end plates form closing plates and the intermediate plates are structured so that the stack of intermediate plates delimit grooves extending over the entire length of the heat pipe channel and having a small width compared to its depth.

For this, in an exemplary embodiment, the heat pipe comprises at least three intermediate plates, two first plates each having an opening of small transverse dimension and a second plate having an opening of large dimension transversely to the length of the heat pipe. Thus the second plate defines with the first two plates two grooves. The width and depth of the capillary channels are fixed, respectively, by the thickness of the second plate and the difference between the transverse dimensions of the openings of the first and second plates. In addition, the bottom of the grooves advantageously has corners delimited by flat surfaces.

Thanks to the invention, a small groove width is chosen, which allows a high capillary pressure. In addition, it is advantageously possible to choose a large width-to-depth ratio of the grooves, the loss of capillary pressure is then reduced.

The capillary pumping effect is then improved, it follows that the limit power that can carry the heat pipe is increased.

Advantageously, the heat pipe has several channels, each channel being delimited by a series of openings made in the plates, each channel advantageously comprising at least one groove.

In other words, the grooves are delimited by stacked plates. Thus the depth and the width of the grooves are obtained separately, the limitations of the depth to width ratio which then arise, for example in the case of production by extrusion or chemical etching, do not arise.

The present invention therefore relates to a capillary pumped heat pipe comprising a first end intended to be heated and a second end intended to be cooled, and a sealed enclosure extending between the first end and the second end, the enclosure comprising a stack of plates, said stack comprising two closure plates, and intermediate plates between the closure plates, each intermediate plate comprising at least one opening, the edges of which partially define a channel. The openings of at least three intermediate plates are dimensioned so that they delimit at least one groove extending between the first end and the second end of the heat pipe, said groove having a width in a direction of the stack less or equal to the depth in the direction of the plane of the plates.

The ratio between the depth and the width of the groove is advantageously between 1 and 80.

Each intermediate plate can have p openings so that the stack of plates delimits p channels.

In an exemplary embodiment, among the three intermediate plates, one is disposed between the other two intermediate plates and is in mechanical contact with the other two intermediate plates.

At least one edge of the opening of the intermediate plate disposed between the two other intermediate plates can form the bottom of at least one groove, and the edges of the openings of the two other intermediate plates delimiting the groove are wavy or sawtooth .

The channel may have two lateral faces, said three intermediate plates delimiting a groove in each lateral face.

The intermediate plates may comprise n first intermediate plates and η + 1 second intermediate plates, the first n intermediate plates each comprising at least one opening of width L1, the η + 1 second intermediate plates each comprising at least one opening of width L2, the width L1 being greater than the width L2, and each first intermediate plate being received between two second intermediate plates, each pair of first successive intermediate plates defining with a second intermediate plate disposed between the first intermediate plates of said pair two grooves facing each other.

The capillary pumped heat pipe may include heat exchange means at the first end and / or second end. The heat exchange means at the second end may include one or more fins in thermal contact with at least one of the closure plates.

The heat exchange means may include a fluid circuit in thermal contact with at least one of the end plates, said circuit being formed by a plate structured so as to delimit channels, said channels being closed by said closure plate and a additional closure plate, the heat exchange means also comprising means for supplying coolant to said fluid circuit.

At least one of the end plates has a surface greater than that of the intermediate plates in a direction transverse to the stack so as to form thermal diffusers.

The present invention also relates to a method for manufacturing a capillary pumped heat pipe comprising, from plates of given external dimensions:

production of at least one opening in each of the plates, stacking of said plates so that the openings delimit a channel and at least three intermediate plates delimit at least one groove extending between the first end and the second end, placed at the ends of the stack in the direction of stacking of closure plates, securing of said plates so as to delimit a sealed enclosure, partial filling of the channel with a fluid in liquid form and sealed closure of the channel.

For example, the plates have an aluminum alloy at their core and on its outer faces an eutectic aluminum alloy with a melting point lower than that of the aluminum alloy with a core and in which the connection is obtained by eutectic brazing .

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be better understood on the basis of the description which follows and of the appended drawings in which:

FIG. IA is a side view of an exemplary embodiment of a capillary pumped heat pipe,

FIG. 1B is a cross-sectional view of the heat pipe of FIG. 1A along the plane A-A,

FIG. 2 is an exploded view of the heat pipe of FIGS. 1A and 1B,

FIG. 3A is a schematic representation of the menisci in the heat pipe of FIGS. IA, IB and 2 at the level of the evaporator,

FIG. 3B is a schematic representation of the menisci in the heat pipe of FIGS. IA, IB and 2 at the level of the condenser,

FIG. 4 is a cross-sectional view of a variant of the heat pipe of FIGS. IA and IB,

FIG. 5 is a cross-sectional view of another exemplary embodiment of a heat pipe comprising several channels,

FIG. 6 is an exploded view of the heat pipe of FIG. 5,

FIGS. 7A and 7B are top views of intermediate plates of another embodiment of a heat pipe,

FIG. 8 is an exploded view of the heat pipe comprising the intermediate plates of FIGS. 7A and 7B,

FIG. 9 is a detailed view of a groove in the heat pipe in FIG. 8,

FIG. 10 is a detailed view of a groove according to a variant of FIG. 8,

FIG. 11 is a view of one end of a heat pipe according to another exemplary embodiment,

FIG. 12 is a top view of an intermediate plate according to another exemplary embodiment,

FIG. 13 is a cross-sectional view of a heat pipe according to another exemplary embodiment comprising thermal diffusers,

FIG. 14 is a perspective view of another exemplary embodiment of a heat pipe according to the invention distributed in several planes,

FIGS. 15A to 15F are perspective views of examples of fins applicable to a heat pipe according to the invention,

FIG. 16 is an exploded view of a heat pipe according to an exemplary embodiment comprising a heat exchanger at the level of the absorber,

FIG. 17A is a cross-sectional view of a heat pipe of the prior art,

FIG. 17B is a top view of a stack of intermediate plates of a heat pipe according to an example of the present invention,

- Figure 18 is a graph representing the capillary limit variations Le in Watt as a function of the inclination of the heat pipe in the case of the heat pipe in Figure 17A (II) and the heat pipe in Figure 17B (I) using water as working fluid, this for a temperature of 60 ° C,

- Figure 19 is a graph representing the maximum power in Watt as a function of the temperature of the heat pipe in the case of the heat pipe of Figure 17A (IΓ) and the heat pipe of Figure 17B (Γ) using acetone as working fluid , this at zero angle of inclination with respect to the horizontal.

FIG. 20 is a cross-sectional view of another exemplary embodiment of a heat pipe according to the invention,

The representations are not necessarily to scale and the proportions between a sectional view and a side view for example are not necessarily respected.

DETAILED PRESENTATION OF PARTICULAR EMBODIMENTS

In FIG. 1A, one can see a capillary pumped heat pipe C1 seen from the outside extending along a longitudinal axis X.

In the present application, the longitudinal direction is that given by the X axis.

The heat pipe Cl comprises a sealed enclosure 2 extending along the longitudinal axis X and comprising a first longitudinal end 4 and a second longitudinal end 6. The first end 4 is for example intended to be disposed at a heat source SC. The first end is designated as an evaporator, and the second end 4 is for example intended to be placed at the level of a cold source SF. The second end is designated condenser.

The heat source is for example an electrical or electronic component, a heat storage, an exothermic chemical reactor. The heat sinks of the fins in forced convection, cold plates in single or two-phase flow, a cold storage, an endothermic chemical reaction ...

The heat pipe advantageously has a shape such that it extends in the XY plane, so as to have faces 7.1, 7.2, parallel to the XY plane, having a large surface promoting heat exchanges with the heat source and the source. cold.

The heat pipe is in contact with the heat source and the cold source on one or both sides 7.1, 7.2 of large area. The faces 7.1, 7.2 of larger surface are in the example shown orthogonal to the direction Z.

In FIG. 1B, a cross-sectional view of the heat pipe C1 can be seen.

The heat pipe C1 has a channel 8 extending along the longitudinal axis X and grooves 10 extending along the longitudinal axis X on either side of the channel 8 in a direction Y orthogonal to the X axis.

The grooves 10 are formed in the side walls 8.1, 8.2 of the channel 8. The side walls are considered with respect to the longitudinal direction X and are located in planes intersecting the planes of the faces 7.1, 7.2 of the largest area of the heat pipe.

The heat pipe enclosure includes a stack E of plates delimiting the channel 8 and the grooves 10.

The stack E comprises two end plates 12 situated at the ends of the stack in a direction Z orthogonal to the directions X and Y. The end plates 12 are intended to close the channel 8 and are also designated “closing plates ".

The stack comprises intermediate plates 14,16 arranged between the end plates 12. The intermediate plates comprise first intermediate plates 14 and second intermediate plates 16, the second intermediate plates 16 alternate with the first intermediate plates 14.

In this example, all the plates 12, 14, 16 have the same external dimensions, the stack is then of rectangular parallelepiped shape.

Each first intermediate plate 14 has a thickness el, and has an opening 18 extending in the direction X and in the direction Y. In this example, the opening 18 has a rectangular shape having a dimension 11 in the direction X and a dimension L1 in direction Y.

Each second intermediate plate 16 has a thickness e2 and has an opening 20 extending in the direction X and in the direction Y. In this example, the opening 20 has a rectangular shape and has a dimension 12 in the direction X and a dimension L2 in direction Y.

The dimensions 11 and 12 are equal or close and correspond to the length of the channel 8.

The dimension L1 is less than the dimension L2.

Because of the different dimensions L1 and L2, the stack of two first plates on either side of a second plate delimit two grooves 10 as can be seen in FIGS. 1B and 3.

Each first plate participates in delimiting grooves 10.

The grooves have a thickness equal to the thickness e2 of the second plate 16 and a depth equal to (L1-L2) / 2, considering that the grooves 10 on either side of the axis X have the same depth and that the openings are centered relative to the edges of the plates.

Thus it is easy to produce grooves whose depth to thickness ratio is large, even very large. Indeed, the depth and the thickness being fixed separately during different stages, there is no limitation due to the manufacturing process unlike extrusion and etching.

It is possible to produce second very thin plates and / or openings between the first and second plates of very different dimensions L1, L2.

For example, the openings are made by punching, cutting, for example with a laser or a water jet.

By producing fine and deep grooves relative to their thickness, a high capillary pressure and a low pressure loss are obtained, therefore an improved capillary pumping compared to the capillary pump heat pipes of the prior art. The liquid flows more easily from the condenser to the evaporator, regardless of gravity.

The capillary pressure is the pressure difference between the vapor phase and the liquid phase in the vicinity of the meniscus.

In FIG. 3A, we can see the menisci M represented in the grooves 10 at the level of the evaporator, and in FIG. 3B at the level of the condenser. The capillary pressure is inversely proportional to the radius of curvature of the meniscus. This radius of curvature is very large in the condenser, and is significantly smaller in the evaporator.

By increasing the depth of the grooves, the cross section of the liquid in the grooves is increased, which reduces the pressure losses and pushes the capillary limit.

In addition, due to the production of the grooves by stacking plates, the bottom of the grooves has substantially straight angles which is favorable to capillary action, unlike the rounded corners of the grooves obtained by extrusion or etching for example.

The heat pipe is filled with a two-phase fluid, it may be a fluid well known to those skilled in the art. This is chosen for example as a function of the operating and storage temperature range of the device, as a function of the stresses due to the pressure, the flammability, the toxicity of the fluid and the chemical compatibility between the fluid and the material. forming the heat pipe.

For example, for a heat pipe made of aluminum alloy assembled by eutectic brazing, ammonia, acetone, methanol, n-heptane, R134a or other fluorinated refrigerants can be used as the fluid.

The operation of the heat pipe will now be explained.

The liquid is evaporated on the evaporator and the generated vapor circulates in the central channel towards the condenser. At the condenser, the vapor condenses. The liquid circulates in the grooves towards the evaporator. The curvature of the meniscus at the evaporator causes a difference in capillary pressure between the evaporator and the condenser, favoring the liquid flow towards the evaporator and the vapor flow towards the condenser.

By making fine and deep grooves, the radius of curvature of the meniscus is reduced on the evaporator, which increases the capillary pressure and therefore the pumping of the liquid towards the evaporator.

Furthermore, the technique of manufacturing by stacking plates makes it possible to obtain a high depth / width ratio of the grooves, which makes it possible to increase the liquid passage section of the grooves and therefore to reduce the loss of liquid pressure.

Advantageously, the width of the grooves is between 0.05 mm and 6 mm, and can reach 0.05 mm. It should be noted that in the case of the heat pipe of the state of the art obtained by extrusion, the width of the grooves is at least of the order of 0.2 mm for small diameters of heat pipe, for example of smaller inside diameter at 10 mm, and around 0.5 mm for larger diameters

Advantageously, the depth of the grooves is between 1 mm and 4 mm, and is very advantageously equal to 3 mm.

The depth / width ratio of the grooves can reach at least 20, or even more with grooves of 0.05 mm in width. In the case of the state of the art heat pipe obtained by extrusion, the depth / width ratio is of the order of 1.

The distance between the evaporator and the condenser can vary from a few centimeters to a few meters.

The heat pipe according to the invention can be made of different materials such as, for example an aluminum alloy, copper, stainless steel. The material or materials used for the manufacture of the heat pipe are chosen according to the constraints of mass, assembly, the required robustness ...

The assembly technique of the sheets depends on the material.

For example, in the case of aluminum alloy plates, it is possible to use vacuum brazing with clad sheets, brazing in a salt bath, brazing under inert gas, ultrasonic welding, friction-kneading welding ( Friction Stir Welding), collage ...

In the case of copper, stainless steel or superalloy plates, diffusion welding, diffusion brazing, bonding, etc. can be used.

In the case of stainless steel plates, super alloys, diffusion welding, diffusion brazing, bonding, etc. can be used.

For example, the assembly of aluminum alloy plates is obtained by eutectic brazing. Aluminum alloy plates are used in known manner, one or both faces of which are or are coated with an aluminum alloy with a lower melting point.

For example, an alloy sheet of the AA3xxxx series with a core is used, with a coating with a eutectic alloy of the AA4xxxx series comprising silicon with a lower melting point.

The coating is typically done by a roll-bond technique.

The total thickness of the plates is typically from 0.05 mm to 5 mm, with a coating typically of 5% to 10% of the total thickness.

By hot pressing two aluminum plates thus coated at a temperature higher than the melting temperature of the eutectic, but lower than the temperature of the core alloy, the eutectic alloy at the bottom surface and forms a brazing alloy tight assembly between the two plates.

In FIG. 4, an exemplary embodiment of a heat pipe C2 can be seen comprising two first intermediate plates 16 and a second intermediate plate 14.

In Figures 5 and 6, we can see a heat pipe C3 according to another embodiment. The heat pipe C3 has several channels 108 arranged one next to the other.

As is particularly visible in Figure 6, the heat pipe C3 has two closure plates 112, a plurality of stacked plates, the intermediate plates 114 and 116 have as many openings as channels.

In the example shown, all the second intermediate plates 116 have the widest openings so that the lateral edges of the openings form the bottom of the grooves and all the first intermediate plates 114 have the narrowest openings, so that the faces first plates form the lateral sides of the grooves.

As a variant, intermediate plates 114 could have the widest openings and the narrowest openings as well as the plates 116.

The heat pipe C3 increases the transmitted heat flow and / or the exchange surface.

Alternatively, the different channels may not have the same number of grooves and / or the same distribution of grooves.

In the examples described above, the edges of the openings defining the grooves are straight and parallel to each other.

In FIG. 7A, one can see first intermediate plates 214 comprising openings 220 comprising corrugated lateral edges 220.1, and in FIG. 7B one can see second intermediate plates 216 comprising openings 218 with straight lateral edges 218.1.

In FIG. 8, an exploded view of the heat pipe C4 can be seen with several second intermediate plates 216 alternating with first intermediate plates 214 between two end plates 212.

In Figure 9, we can see a detailed view of a channel obtained and a groove 210. The groove is wavy in the XY plane.

This shape increases the length of the triple line, especially in the evaporator zone, which increases the exchange coefficient in evaporation.

At the level of the condenser, the corrugated shape makes it possible to obtain walls not wetted by the film of condensation at the tops of the corrugations. This also makes it possible to increase the condensation exchange coefficient by minimizing the interface resistance of the condensation film.

In this example, the bottom of the grooves is straight. Alternatively, it can also be corrugated.

In FIG. 10, a variant can be seen, in which the edges 320.1 of the openings are sawtooth. The grooves 310 are also sawtooth in the XY plane. As with the corrugated grooves, the exchange coefficients in condensation and evaporation are increased.

It will be understood that any other form is possible. In view of the embodiment of the openings, great freedom in the shape of the edges exists.

It can even be envisaged to produce straight grooves in one side face of the channel and corrugated grooves in the other opposite face.

According to another example, the channel has a section other than rectangular, it is for example trapezoidal.

In the examples described above, all the plates have the same dimensions, it follows that the heat pipe has a parallelepiped shape. According to another example, the surface of the plates can vary. It can be envisaged that the surface of the plates decreases in the Z direction, as shown in FIG. 11.

It is also conceivable that the width of the intermediate plates is variable along the direction X, for example to produce a condenser with a larger surface area than the evaporator, as shown in FIG. 12 representing a first intermediate plate 414. The openings are shaped so as to cover the entire surface, they are not parallel.

In one example, only one of the lateral faces of the channel has grooves. It is also possible to envisage a different number of grooves between the two lateral faces. In another exemplary embodiment, the grooves 610 in one side face are offset with respect to the grooves in the other side face as shown diagrammatically in FIG. 20. This exemplary embodiment allows the same type of sheet to be used to form all the intermediate plates, for this it suffices to turn each head-to-tail plate alternately.

According to another example, the grooves do not have the same depth in the same channel and / or from one channel to another.

In Figure 13 we can see another example of C5 heat pipe. This is close to the C3 heat pipe, it also includes thermal diffusers or "spreader" in English terminology extending parallel to the XY plane. In this example, the thermal diffusers are in one piece with the closure plates and extend symmetrically on either side of the channel. These diffusers have the effect of spreading the heat flow over a wider area and increasing the overall efficiency of the thermal system.

As a variant, only one of the two closure plates comprises diffusers and / or diffusers are provided only on one side of the XZ plane and / or the diffusers have different surfaces on either side of the XZ plane. It can be envisaged that the size of the diffuser (s) is reduced, for example in the direction X.

In FIG. 14, we can see another example of embodiment in which the heat pipe C6 does not have a straight shape, it comprises two straight portions DI and D2 oriented at right angles to each other. In addition, the portions DI and D2 extend in orthogonal planes. The DI portion extends in the XY plane and the D2 portion extends in the XZ plane. The orientation of the portions DI and D2 with respect to each other is for example obtained by folding after stacking of the plates and their joining. PI indicates the fold.

The C6 heat pipe can be shaped to suit the application. The heat pipe can have several folds.

In this example, the portion DI forms the evaporator and the portion D2 forms the condenser and is provided on its outer surfaces with fins Al forming a radiator allowing the heat to be removed. The radiator is for example in natural convection or in forced convection. In this example, the fins are provided on the two large surface faces of the condenser. As a variant, fins on a single surface could be envisaged. On figure 14, one can see a queusot Q of filling of the heat pipe C6.

In this example, the fins have flat plates perpendicular to the faces of the condenser. Any other form is possible.

It will be understood that a heat pipe such as that of Figure IA could be curved instead of being straight without departing from the scope of the present invention.

In FIGS. 15A to 15F are shown pleated fins according to other exemplary embodiments applicable to the present invention.

According to other examples, the fins are extruded fins, skivated fins, spiked fins, molded fins, fins fixed by knurling, fins produced by 3D printing, or any other fin obtained by an extension technique. surface well known to those skilled in the art.

As a variant, a cooling circuit is integrated directly into the heat pipe C7 as shown in FIG. 16.

The heat pipe has a cooling circuit 524 in which a heat transfer fluid circulates. The cooling circuit is directly in contact with the condenser. In the example shown, the cooling circuit 524 is formed by an additional plate 526, in which grooves 528 are formed defining the side walls of the circuit, and the closure plate 512 and an additional closure plate 530 form the walls d end of the cooling system. The additional closure plate 530 has two orifices 532 each opening at one end of the circuit and allowing the circulation of the heat transfer fluid.

The heat transfer fluid can be a liquid or a gas.

According to another example, it is a two-phase circuit.

Such a circuit can also be used to form the heat source at the evaporator.

We will now compare the performance of a heat pipe according to the invention and a capillary pumped heat pipe of the prior art.

Consider a heat pipe of the prior art cylindrical obtained by extrusion and having longitudinal grooves 610, as shown in Figure 17A.

Each heat pipe has a length of the evaporator of 50 mm, a length of the adiabatic zone of 100 mm, a length of the condenser of 110 mm

Each heat pipe is made of copper. The temperature in the adiabatic zone of the heat pipe is 60 ° C; i.e. the average vapor temperature of the heat pipe.

The state of the art heat pipe has the following characteristics:

Inner diameter Di: 10 mm

Outer Diameter From: 12 mm

Groove width Le: 0.5 mm

Groove depth Pe: 0.5 mm

Number of grooves: 44

The heat pipe according to the invention has the following characteristics (FIG. 17B):

External width Le: 12 mm

External height He: 12 mm

Width of grooves L: 0.5 mm

Groove depth P: 2 mm

Number of grooves: 15.

In Figure 18, we can see the variation of the capillary limit Le in Watt as a function of the angle of inclination a of the heat pipe in °, i.e. the inclination of the X axis relative to the horizontal direction. Curve I corresponds to the invention and curve II to the heat pipe according to the state of the art. Negative tilt values correspond to positions of the heat pipe in which the evaporator is above the condenser. The fluid is water.

It is found that the heat pipe according to the invention is more efficient than the heat pipe of the prior art, whatever the inclination of the heat pipe.

In Figure 19, we can see maximum power P in Watt as a function of temperature T in ° C. The curve Γ corresponds to the invention and the curve 11 'to the heat pipe according to the state of the art. The fluid is acetone. The angle of inclination with respect to the horizontal is zero.

It is found that the heat pipe according to the invention is more efficient than the heat pipe of the prior art, whatever the temperature of the heat pipe.

It will be understood that the different examples and variant embodiments are not mutually exclusive and can be combined in whole or in part.

An example of an embodiment method will now be described.

Plates of a given material are cut according to the external shape desired for the heat pipe.

In a next step, the openings are made in all the intermediate plates. The openings are made for example by punching, laser cutting, by water jet cutting or by through chemical etching ... openings of different dimensions are made in the different plates so that once assembled grooves are formed.

The plates are then stacked so as to delimit the grooves, closing plates are arranged at the ends of the stack to close the channel or channels. Optionally cooling channels are provided on one or both sides of the stack.

The plates are assembled, the assembly technique being chosen as a function of the material or materials of the plates, for example welding, brazing, bonding ... the assembly of the plates is waterproof.

The heat pipe is then filled. A filling orifice was provided in one of the opening plates during the manufacture of the plates. The fluid is chosen according to the operating conditions of the heat pipe (operating temperature, etc.) and the compatibility with the material or materials of the heat pipe.

Claims (13)

1. Capillary pumped heat pipe comprising a first end (4) intended to be heated and a second end (6) intended to be cooled, and a sealed enclosure (2) extending between the first end (4) and the second end (6), the enclosure comprising a stack of plates, said stack comprising two closing plates (12), and intermediate plates (14, 16, 216, 214) between the closing plates (12), each intermediate plate ( 14, 16, 216, 214) comprising at least one opening, the edges of which partially define a channel (8), and in which the openings of at least three intermediate plates (14, 16, 216, 214) are dimensioned so that they define at least one groove (10, 210) extending between the first end (4) and the second end (6) of the heat pipe, said groove (10, 210) having a width in a direction of the stack less than or equal to the depth in the directio n of the plane of the plates (14,16, 216, 214). 2. Capillary pumping heat pipe according to claim 1, in which the ratio between the depth and the width of the groove (10) is between 1 and 80. 3. Capillary pumping heat pipe according to claim 1 or 2, wherein each intermediate plate has p openings so that the stack of plates delimits p channels. 4. Capillary pumping heat pipe according to one of claims 1 to 3, wherein among the three intermediate plates (14,16), one is disposed between the two other intermediate plates and is in mechanical contact with the other two plates dividers. 5. Capillary pumping heat pipe according to claim 4, in which at least one edge of the opening of the intermediate plate (216) disposed between the two other intermediate plates (214) forms the bottom of at least one groove (210). , and in which the edges (220.1) of the openings of the two other intermediate plates (214) delimiting the groove (210) are wavy or sawtooth. 6. Capillary pumping heat pipe according to one of the preceding claims, in which the channel (10) has two lateral faces (8.1, 8.2), said three intermediate plates delimiting a groove (10) in each lateral face (8.1, 8.2) . 7. Capillary pumping heat pipe according to one of claims 1 to 6, in which the intermediate plates comprise n first intermediate plates (14) and η + 1 second intermediate plates (16), the n first intermediate plates (14) each comprising at least one opening of width L1, the η + 1 second intermediate plates -16) each comprising at least one opening of width L2, the width L1 being greater than the width L2, and each first intermediate plate (14) being received between two second intermediate plates (16), each pair of successive first intermediate plates (16) defining with a second intermediate plate (16) disposed between the first intermediate plates (14) of said pair two facing grooves (10). 8. Capillary pumping heat pipe according to one of claims 1 to 7, comprising heat exchange means at the first end and / or second end. 9. Capillary pumped heat pipe according to claim 8, wherein the heat exchange means at the second end comprise one or more fins (Al) in thermal contact with at least one of the closure plates. 10. Capillary pumping heat pipe according to claim 8 or 9, in which the heat exchange means (524) comprise a fluidic circuit in thermal contact with at least one of the end plates, said circuit being formed by a structured plate. (526) so as to delimit channels (528), said channels (528) being closed by said closure plate and an additional closure plate (530), the heat exchange means also comprising means (532) for supplying in coolant said fluid circuit. 11. Capillary pumping heat pipe according to one of claims 1 to 10, in which at least one of the end plates has a surface greater than that of the intermediate plates in a direction transverse to the stack so as to form thermal diffusers (120). 12. Method for manufacturing a capillary pumped heat pipe comprising, from plates of given external dimensions: - Creation of at least one opening in each of the plates, - Stacking of said plates so that the openings delimit a channel and at least three intermediate plates delimit at least one groove extending between the first end and the second end, - Positioning at the ends of the stack in the direction of the stack of closure plates. - Securing of said plates so as to delimit a sealed enclosure, - Partial filling of the channel with a fluid in liquid form and tight closure of the channel. 13. The manufacturing method according to claim 12, in which the plates comprise an aluminum alloy at its core and on its outer faces an eutectic aluminum alloy with a melting point lower than that of the aluminum alloy at its core and in which the connection is obtained by eutectic brazing.